# 计科1813-38-和泽妮
i=int(input("请输入你的成绩："))
if i<=100 and i>=90:
    print("A")
elif i>=80:
    print("B")
elif i>=70:
    print("C")
elif i>=60:
    print("D")
elif i<60:
    print("不及格!")
else:
    print("输入错误")            
